Voglibose-inspired synthesis of new potent α-glucosidase inhibitors N-1,3-dihydroxypropylaminocyclitols

Enantioselective Synthesis of Nabscessin C

Enantioselective synthesis of nabscessin C (1), an aminocyclitol amide with antimicrobial activity, is reported. Starting from myo-inositol, (+)-nabscessin C was synthesized in 12 isolation steps. Desymmetrization of 2-deoxygenated 4,6-dibenzylinositol was achieved using lipase from porcine pancreas (PPL), and the stereochemistry was established by X-ray crystallography. This method has the potential for synthesizing other cyclitol-derived compounds.

Synthesis and evaluation of ent-Conduramine C-1 derivatives as α-glucosidase inhibitors via CSI-mediated amination reaction

Concise synthesis of ent-conduramine C-1 and its derivatives has been achieved by using commercially available d-ribose. The key steps in the synthesis are regioselective and diastereoselective amination of polybenzyl ethers by chlorosulfonyl isocyanate (CSI), chelation-controlled carbonyl addition, and intramolecular olefin metathesis. All of the synthesized compounds were evaluated for inhibitory activity against α-glucosidase. The derivatives 18 (IC₅₀ = 0.65 ± 0.03 mM) and 19 (IC₅₀ = 0.26 ± 0.01 mM) were identified to be more potent than well-known α-glucosidase inhibitor acarbose (IC₅₀ = 1.05 ± 0.17 mM) as a positive control.

Identification of raloxifene as a novel α-glucosidase inhibitor using a systematic drug repurposing approach in combination with cross molecular docking-based virtual screening and experimental verification

α-Glucosidase is a promising target for the treatment of diabetes. Drug repurposing can increase the chances of discovering an active inhibitor. Therefore, this study aimed to identify potential α-glucosidase inhibitor using drug repurposing and in silico strategies. We identified critical amino acid residues of the three α-glucosidase proteins. Based on cross molecular docking studies of three α-glucosidase proteins and drugs in the FDA database, we screened hits with the favorable binding affinities and modes targeting the three proteins. Subsequently, an in vitro activity assay showed that raloxifene was an excellent inhibitor of α-glucosidase. Moreover, molecular dynamics simulations of raloxifene and three proteins were performed to assess the stability of the protein-hit systems in physiological conditions and clarify protein-hit interactions. We also performed the binding free energy calculation, Hirshfeld surface and alanine scanning mutagenesis analyses. These results demonstrated that binding between raloxifene and the three proteins was stable, and the critical amino acid residues of the three proteins formed stable contacts with raloxifene. The molecular mechanisms agree well with its activity, reinforcing that raloxifene is a candidate α-glucosidase inhibitor. Our study smoothes the path for the development of novel a-glucosidase inhibitors with high efficacy and low toxicity for the treatment of diabetes.

An overview of therapeutic potential of N-alkylated 1-deoxynojirimycin congeners

Polyhydroxylated alkaloids display a wide range of biological activities, suggesting their use in the treatment of various diseases. Their most famous representative, 1-deoxynojirimycin (DNJ), is a natural product that shows α- and β-glucosidase inhibition. This molecule has been since converted into two clinically approved drugs i.e., Zavesca® and Glyset®, targeting type I Gaucher's disease and type II diabetes mellitus, respectively. This review examines the therapeutic potential of important DNJ congeners reported in last decade and presents concise mechanism of glycosidase inhibition. A brief overview of substituents conjugation's impact on DNJ scaffold (including N-alkylated DNJ derivatives, mono-valent, di-valent and multivalent DNJ congeners, N-[5-(adamantan-1-yl-methoxy)-pentyl]-1-deoxynojirimycin (AMP-DNM) look alike DNJ based lipophilic derivatives, AMP-DNM based neoglycoconjugates, DNJ click derivatives with varying carboxylic acids and aromatic moieties, conjugates of DNJ and glucose, and N-bridged DNJ analogues) towards various enzymes such as α/β glucosidase, porcine trehalase, as F508del-CFTR correctors, α-mannosidase, human placental β-glucocerebrosidase, N370S β-GCase, α-amylase and insect trehalase as potent and selective inhibitors have been discussed with potential bioactivities, which can provide inspiration for future studies.

Natural Triterpenoids Isolated from Akebia trifoliata Stem Explants Exert a Hypoglycemic Effect via α-Glucosidase Inhibition and Glucose Uptake Stimulation in Insulin-Resistant HepG2 Cells

The inhibition of α-glucosidase activity is a prospective approach to attenuate postprandial hyperglycemia in the treatment of type 2 diabetes mellitus (T2DM). Herein, the inhibition of α-glucosidase by three compounds T₁ -T₃ of Akebia trifoliata stem, namely hederagenin (T₁ ), 3-epiakebonoic acid (T₂ ), and arjunolic acid (T₃ ) were investigated using enzyme kinetics and molecular docking analysis. The three triterpenoids exhibited excellent inhibitory activities against α-glucosidase. T₁ -T₃ showed the strongest inhibition with IC₅₀ values of 42.1±5.4, 19.6±3.2, and 11.2±2.3 μM, respectively, compared to the acarbose positive control (IC₅₀ =106.3±8.2). Enzyme inhibition kinetics showed that triterpenoids T₁ -T₃ demonstrated competitive, mixed, and noncompetitive-type inhibition against α-glucosidase, respectively. The inhibition constant (K_i ) values were 21.21, 7.70, and 3.18 μM, respectively. Docking analysis determined that the interaction of ligands T₁ -T₃ and α-glucosidase was mainly forced by hydrogen bonds and hydrophobic interactions, which could result in improved binding to the active site of the target enzyme. The insulin resistant (IR)-HepG2 cell model used in this study (HepG2 cells exposed to 10^-7  M insulin for 24 h) and glucose uptake assays showed that compounds T₁ -T₃ had no cytotoxicity with concentrations ranging from 6.25 to 25 μM and displayed significant stimulation of glucose uptake in IR-HepG2 cells. Thus, triterpenoids T₁ -T₃ showed dual therapeutic effects of α-glucosidase inhibition and glucose uptake stimulation and could be used as potential medicinal resources to investigate new antidiabetic agents for the prevention or treatment of diabetes.

Altering the inhibitory kinetics and molecular conformation of maltase by Tangzhiqing (TZQ), a natural α-glucosidase inhibitor

Background

Tangzhiqing (TZQ), as a potential α-glycosidase inhibitor, possesses postprandial hypoglycaemic effects on maltose in humans. The aim of this study was to investigate the mechanisms by which TZQ attenuates postprandial glucose by interrupting the activity of maltase, including inhibitory kinetics and circular dichroism studies.

Methods

In this study, we determined the inhibitory effect of TZQ on maltase by kinetic analysis to determine the IC₅₀ value and enzyme velocity studies and line weaver-burk plot generation to determine inhibition type. Acarbose was chosen as a standard control drug. After the interaction with TZQ and maltase, secondary structure analysis was conducted with a circular dichroism method.

Results

TZQ showed notable inhibition activity on maltase in a reversible and competitive manner with an IC₅₀ value of 1.67 ± 0.09 μg/ml, which was weaker than that of acarbose (IC₅₀ = 0.29 ± 0.01 μg/ml). The circular dichroism spectrum demonstrated that the binding of TZQ to maltase changed the conformation of maltase and varied with the concentration of TZQ in terms of the disappearance of β-sheets and an increase in the α-helix content of the enzyme, similar to acarbose.

Conclusions

This work provides useful information for the inhibitory effect of TZQ on maltase. TZQ has the potential to be an α-glycosidase inhibitor for the prevention and treatment of prediabetes or mild diabetes mellitus.

Asymmetric Synthesis of Nabscessin A from Inositol and d-Camphor

An enantiomer of nabscessin A (1), an aminocyclitol amide with antimicrobial activity, was synthesized from myo-inositol and dimethyl d-camphor acetal in 14 steps. Formal synthesis of natural nabscessin A was also achieved through the new approach to access both enantiomers of 4,5-di-O-benzyl-myo-inositol, derived from the same set of starting materials. This synthesis features utilizations of the existing framework of myo-inositol and a regioselective esterification.

Efficient and Highly Stereoselective Syntheses of (+)-proto-Quercitol and (-)-gala-Quercitol Starting from the Naturally Abundant (-)-Shikimic Acid

Efficient and highly stereoselective syntheses of (+)-proto-quercitol and (-)-gala-quercitol starting from the naturally abundant (-)-shikimic acid were described in this article. (-)-Shikimic acid was first converted to the key intermediate by eight steps in 53% yield. It was then converted to (+)-proto-quercitol by three steps in 78% yield and was also converted to (-)-gala-quercitol by five steps in 63% yield. In summary, (+)-proto-quercitol and (-)-gala-quercitol were synthesized from (-)-shikimic acid by 11 and 13 steps in 41 and 33% overall yields, respectively.

Furofuran lignans as a new series of antidiabetic agents exerting α-glucosidase inhibition and radical scarvenging: Semisynthesis, kinetic study and molecular modeling

A new series of furofuran lignans containing catechol moiety were prepared from the reactions between lignans and a variety of phenolics. All 22 products obtained were evaluated against three different α-glucosidases (maltase, sucrase and Baker's yeast glucosidase) and DPPH radical. Of furofuran lignans evaluated, β-14, having two catechol moieties and one acetoxy group, was the most potent inhibitor against Baker's yeast, maltase, and sucrase with IC₅₀ values of 5.3, 25.7, and 12.9 µM, respectively. Of interest, its inhibitory potency toward Baker's yeast was 28 times greater than standard drug, acarbose and its DPPH radical scavenging (SC₅₀ 11.2 µM) was 130 times higher than commercial antioxidant BHT. Subsequent investigation on mechanism underlying the inhibitory effect of β-14 revealed that it blocked Baker's yeast and sucrase functions by mixed-type inhibition while it exerted non-competitive inhibition toward maltase. Molecular dynamics simulation of the most potent furofuran lignans (4, α-8b, α-14, and β-14) with the homology rat intestinal maltase at the binding site revealed that the hydrogen bond interactions from catechol, acetoxy, and quinone moieties of furofuran lignans were the key interaction to bind tightly to α-glucosidase. The results indicated that β-14 possessed promising antidiabetic activity through simultaneously inhibiting α-glucosidases and free radicals.

Quercitol: From a Taxonomic Marker of the Genus Quercus to a Versatile Chiral Building Block of Antidiabetic Agents

Quercitol is a cyclohexanepentol that has been recognized as a biomarker of plants in genus Quercus, which includes oak. As a result of its glucose-like structure, it has been introduced as an alternative chiral building block in the synthesis of several bioactive compounds. Our continuing investigations on the synthesis of antidiabetic agents from quercitol have demonstrated that this chiral synthon can generate diverse structural features with improved hypoglycemic activity.